Huge crack in Antarctic Larsen C Ice Shelf signals collapse

A large, widening crack has appeared in the Larsen B Ice Shelf [Credit: British Antarctic Survey]If a 180 km crack was appearing across continental Europe there may be a sense of public panic. Well, that’s just what is happening across another continent, in Antarctica, where scientists early this year spotted a crack in a lump of floating ice called the Larsen C ice shelf, which is about twice the size of Wales.

A secondary crack, or fork, has now appeared in Larsen C, leaving just 20km of solid ice left preventing it from total collapse. Scientists believe that nothing can now stop the collapse of Larsen C, and when it does break up it will be even more dramatic than the break up of the nearby Larsen B ice shelf in 2002.

Crack

In February, scientists at the British Antarctic Survey reported that they had found a large crack, about 180 km – about the distance between Dublin and Galway – in an ice shelf called the Larsen C Ice Shelf.

This crack has been monitored by scientists over the past few months and they have found that it is widening. More recently, a fork has split away from the main crack, and this secondary crack is heading straight for the open ocean.

The continent of Antarctica is famous, among scientists at least, for having several large shelves of ice around its coastline. These ice shelves are huge, floating platforms of ice, which form i the ocean and are fed ice from the continental landmass.

The Larsen C ice shelf is part of the larger Larsen ice shelf, which is one of the largest in Antarctica and has been breaking up now for a number of decades. The Larsen B, ice shelf, which was about the size of Rhode Island, some people may recall, broke away in 2002.

The area is closely watched by scientists interested in climate change because the western side of Antarctica is the fastest warming area of the world, and an indicate of how fast climate change is happening.

Concern

The ice shelves of western Antarctica were stable for 10,000 years, and it is only in the last 30 years that they have started to break up.

Scientists are very concerned, as with just 20km of ice for the breakaway fork to travel to get to the sea, the breakup of Larsen C appears to be close. When Larsen C breaks away, it will produce the largest iceberg in history, which will be cleaved off the Larsen ice shelf to float off into the southern ocean around Antarctica.

The fact that ice shelves float in the ocean means they are susceptible to changes in ocean temperature. Scientists know that the temperature of the oceans is heating up, and this heat is being transferred, they believe, to the bottom of ice shelves, which can make the ice unstable, fracture and break.

There have been cycles of ice shelves forming, and breaking away throughout Earth’s history, with repeated cycles of warming and cooling. At one point, for example, during the last ice age a large ice sheet existed off the west coast of Ireland.

What is worrying scientists is that the current fracture of Larsen C is mimicking the processes that led to the breakup of Larsen A and B. In those cases there was destabilisation of the front of the ice shelf, where the ice cliffs – as big as the cliffs of moher – meet the open water.

Scientists, like Dr Paul Dunlop, who has studied glaciers, and is based at the School of Geography and Environmental Sciences, Ulster University, Coleraine, is worried that what’s happening could be a sign of something bigger, and far more serious.

Another worry is that if the Larsen ice shelf breaks away that this will expose land based glaciers to the open ocean, meaning they will melt faster.

At the moment, the ice shelves in the western Antarctica are acting like a buffer between the glaciers and the sea, but if that goes, it may be something akin to pulling the plug out of a bath.

Conditions

It tells us that the waters underneath the ice shelves in the western Antarctica are warming. That is worrying because the deep waters around Antarctica were considered to be the last ocean locations to experience global warming, but that now appears to be happening, as deep cold water, cycles up and is warmed.

There will still be climate deniers that will say that the breakup of Larsen C is simply part of a cycle of the formation and breakup of ice shelves that has gone on for millions of years, and that it is not linked to climate change. However, this view is simply that and it is not remotely credible to climate scientists.

Climate scientists believe that the deep ocean waters around Antarctica are starting to warm and that is the source of the problem. This is part of a pattern going in recent decades not just in Antarctic, but around the world, with Alpine and Himalayan glaciers retreating and the Greenland ice sheet thinning for example.

Dangerous

Earlier this year, a British scientific team had been on the Larsen C ice shelf, surveying the seafloor beneath. The information they gathered, and other data, suggested that a break up was likely, so they decided not to set up camp on the ice as would be normal practice. Instead, they made one-off airplane trips from the UK’s Rothera Research Station, as it was considered too dangerous to stay.

It’s getting pretty dangerous for scientists on Antarctica, especially those working on the ice shelves around the continent. In January, the Halley VI British Antarctic Station was shifted – on skis – to a safe remove on health and safety grounds as a result of a crack in the Brunt Ice Shelf that was growing in size just to the north of their futuristic modular facility. The designers deliberately designed the base so that it would sit on stilts with skis and could be moved if required.

Dr Louise Allock, senior lecturer in Zoology at NUI Galway has visited Antarctica for her research into octopuses, corals and sea pens many times over the last 15 to 20 years, and was on a research vessel in the southern ocean off Antarctica when the Larsen B shelf dramatically collapsed in 2002.

She told me what scientists will be watching closely – as the Larsen C collapses – so see whether this has the potential to cause large scale ice shelf collapse.